Communication networks are built of nodes (such as switches, routers, and servers) that are located in facilities typically referred to as central offices (of telephone companies) and data centers (of IT service providers). Each facility constitutes a room in a building, the room holding rows of racks, each rack holding a number of shelves, each shelf holding several printed circuit boards of a node (also called “network element”). Within any given facility, each shelf has width and depth sufficient to fit within a rack of dimensions that are standardized depending on whether the facility is a data center or a telco central office.
For example, a telco rack 110 (FIG. 1) may be a seven foot tall open frame consisting of two posts 111 and 112 separated from each other by 23 inches or 600 mm, mounted on a base 114 and connected at the top by a cross-bar 113. A number of such racks (three are shown in FIG. 1 for illustration, although there are more) usually bolted to the floor of the room, adjacent to one another in a row. Adjacent rows in a room are separated from each other by distances that are of the same order as frame width (e.g. 2 to 3 feet). The just-described inter-row distances are kept small to minimize overhead of the facility (for example, for power backup via a diesel generator and security via human guards).
A shelf 100 (FIG. 1), of such a telco rack or cabinet may conform to Advanced Telecom Computing Architecture (ATCA), a series of industry specification standards for next generation carrier grade communications equipment, such as ATCA 3.0. The ATCA specification defines the physical and electrical characteristics, such as rack and shelf form factors, power, cooling, management interfaces, and the electromechanical specification of ATCA-compliant boards. Such a shelf (also called “chassis”) may hold sixteen printed circuit boards in the front of each shelf, each PCB typically supporting one or more integrated circuit (IC) chips, such as processors, switches, traffic managers, memories, and optionally one or more transceivers. Each printed circuit board has a face plate that forms a portion of a front surface of the shelf. The face plate has openings to accommodate light emitting diodes (LEDs) that are also supported on the printed circuit board. The face plate may carry a legend adjacent to the opening of each LED.
Instead of LEDs, it is also known in the prior art to use a translucent plastic strip as a face plate that has light incident from the back, for example as described in U.S. Pat. No. 3,681,665 which is incorporated by reference herein in its entirety as background.
The inventors of the current patent application believe that there is a need to improve back lit face plates of prior art chassis.